材料期刊网

以单元系二相平衡点为基点,考虑到引入新组分后汽相化学势和晶相键结合能的变化,导出二元系结晶过程的动力学常数表达式。它适用于任何组分配比的二元系。 模拟结果表明:当A,B粒子间的结合键比两个A粒子间的结合键弱时,分凝系数小于1;当A,B粒子间的结合键比两个A粒子间的结合键强时,分凝系数大于1。 随生长速度的增大,分凝系数都趋向于1。

Taking two-phase equilibrium point of the single component system as a basic, an expression for kinetic rate constants of the binary system crystallization was derived in consideration of the changes in the chemical potential of gaseous phase and in the bond combination energy of crystalline phase after a new constituent added. The chemical potential differences caused by both partial pressure and equilibrium temperature shift have been taken into account. Hence, it may be available for any binary system with an arbitrary proportion.The computer simulation was made of the crystallization process for binary systems. It was shown that when the bond between molecules A and B is weaker than that between two A's, the segregation coefficients will be smaller than 1, adding of the new constituent makes the growth slower, and then the chemical potential of vapour must be increased to obtain the equilibrium with crystalline phase. In contrast to this, when the bond between A and B is stronger than that between two A's, the segregation coefficients will be greater than 1, adding of the new constituent makes the growth faster, and then the chemical potential of the vapour must be decreased to obtain the equilibrium with crystalline phase. In both cases, with the increasing growth rate, the segregation coefficients will approach to 1 more and more.All the simulation results seem to be in accordance with the binary system phase diagram and the model seems to be considered correctly.